common: Drop init.h from common header

Move this uncommon header out of the common header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/freescale/imx8mm_evk/spl.c b/board/freescale/imx8mm_evk/spl.c
index f73ade5..3abf6be 100644
--- a/board/freescale/imx8mm_evk/spl.c
+++ b/board/freescale/imx8mm_evk/spl.c
@@ -7,6 +7,7 @@
 #include <cpu_func.h>
 #include <hang.h>
 #include <image.h>
+#include <init.h>
 #include <spl.h>
 #include <asm/io.h>
 #include <asm/mach-imx/iomux-v3.h>